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The first commercially operated cargo ship destined for the International Space Station entered the record books Friday when the station's crew confirmed that SpaceX's Dragon spacecraft was securely docked to the orbiting outpost.

Dragon cleared its first major hurdle of the day Friday when station flight engineer Don Petitt, the mission's grappler-in-chief, captured the Dragon capsule with the station's robotic arm as the craft free-floated some 30 feet from the docking port.

“Houston? Station. Looks like we've got us a dragon by the tail,” Dr. Petitt said as NASA's mission control confirmed that the arm's grip was solid.

Without skipping a beat, he deadpanned, “We're thinking this sim[ulation] went really well. We're ready to turn it around and do it for real,” as applause and hugs broke out in two control rooms – NASA's and SpaceX's at the company's Hawthorne, Calif., headquarters.

Until its conclusion on May 31, the mission remains a test flight – combining into one mission the objectives initially planned for two launches this year. But its success so far signals that a company NASA has helped nurture can perform the difficult feat of lofting a craft capable of catching up with another spacecraft traveling at faster-than-bullet speeds, matching its pace, and safely docking with it – something no other privately-operated spacecraft has done.

Indeed, Dragon was not merely carrying a demonstration payload of roughly 1,000 pounds of food, clothing, and other items to the space station. It was carrying the hopes of a US commercial spaceflight industry aiming to build a thriving space-transportation sector in much the same way fledgling air carriers emerged during the early decades of the 20th Century to build a thriving commercial air-transportation industry.

Over the years, NASA officials have spoken of the “firsts” the US space program has accomplished, said Michael Suffredini, space-station program manager at NASA, at a news briefing Friday afternoon.

“This rates right at the top,” he said of the partnership between NASA and SpaceX. NASA established requirements SpaceX had to meet operating near the space station. Beyond those requirements, he said, “a contractor relatively independent of NASA designed on its own a spacecraft, [then] completely built and tested and flew this spacecraft in a manner that has been remarkable.”

A space-station workout

The rendezvous and docking Friday gave participating space-station crew members a workout.

Although the process of grappling and berthing may look fairly simple, it isn't, notes astronaut Catherine Coleman, who grappled Japan's cargo craft, known by its acronym HTV, on its second supply mission to the station in January 2011. She likens it to trying to pass something from one car to another – when both are traveling at interstate speeds.

“This is truly a momentous accomplishment for SpaceX and for the industry,” said former astronaut and space-station commander Michael Lopez-Alegria, now president of the Commercial Spaceflight Federation in Washington, in a prepared statement.

NASA itself has no small dog in this hunt. In an era of tight budgets and sometimes rancorous debates over the space agency's budget and future, it's looking to commercial companies to take over transportation for people and cargo to and from the space station so it can devote its human-spaceflight resources on exploration beyond low-Earth orbit.

Indeed, Dragon, and a second cargo craft slated for tests later this year and built by Orbital Sciences Corporation, will become the workhorses for space-station resupply efforts throughout the rest of the space-station program, notes Michael Suffredini, NASA's space-station program manager. Although Japan, the European Space Agency, and Russia fly cargo craft to the station, Europe has only two missions left between now and 2014. Japan is slated to launch five more resupply missions through 2015. SpaceX is under contract with NASA to provide 12 flights through 2015. Orion is under contract for eight flights.

The docking, minute by minute

After passing its tests on Thursday, Dragon began its rendezvous approach just before 1:00 a.m. Eastern Daylight Time Friday. Approaching from directly underneath the space station, Dragon reached a way point some 100 feet below the station at 9:13 a.m. Along the way, it had demonstrated its ability to advance and retreat on command – a capability crucial to safe operation at the station.

By 9:53 a.m. Dragon was within thin reach of the space station's robotic arm. Seven minutes later it was firmly in the arm's grip. Andre Kuipers, a station crew member with the European Space Agency, brought the capsule in to its docking port on the stations Harmony module. There, NASA crew member Joe Acaba batted cleanup, overseeing the final bolting of Dragon to the space station.

At 12:02 mission control confirmed that Dragon had become the newest – if temporary – module on the space station.

The nature of the mission as a demonstration flight became apparent as Dragon was making its approach. Controllers either halted its progress temporarily or held it at a way point longer than planned to deal with unexpected glitches in the Dragon's rendezvous sensors.

That issues arose is not unexpected in a test flight, said Holly Ridings, NASA's lead flight director for this mission.

“It took us some time to understand those sensors” given that this was the first time they had been used in space, she acknowledged. “But the Dragon team did a wonderful job of understanding the data they were receiving and working jointly with us to overcome the challenges.”

'Historical step'

For his part, SpaceX's founder and chief designer, Elon Musk, was finding it difficult to convey his sense of the company's singular achievement.

“I don't have words enough to express the level of excitement and elation we feel here at SpaceX for having this work,” he said. “There's so much that could have gone wrong and went right. This really is going to be recognized as a significantly historical step forward in space travel.”

The station crew is slated to open Dragon's hatch Saturday at 7:40 a.m. Eastern Daylight Time. But don't be surprised if the crew cracks the hatch earlier, warns Ms. Riding, “the crew's pretty excited.”

Dragon will remain attached to the station until May 31, when it's scheduled to return to Earth with some 1,400 pounds of cargo.